The invention relates to a shaft, and in particular to a drive shaft including a member made of an elastic material and connecting pieces made of a less-elastic or inelastic second material.
Especially for the transfer of low torques, a shaft which includes a member made of an elastic material and connecting pieces made of a less-elastic or inelastic second material is intended to make possible compensation for an axial and angular offset between connecting parts.
U.S. Pat. No. 2,271,567 describes a coupling piece made of elastic material, having shaped-in connecting pieces made of inelastic, wear-resistant material. The connectors are rings having undercuts provided for rotation prevention on their respective outer peripheries. These rings are embedded, with axially and radially positive engagement, in the elastic basic member material of the shaft. Because a positive engagement within the elastic basic member material of the shaft is present only on the outer periphery of the rings, the danger exists that rotation of the rings inside the basic member material in the presence of torques to be transferred by the shaft will be insufficiently prevented.
A connecting shaft described in U.S. Pat. No. 2,994,213 has an elastic basic member and shaped-in inelastic connecting pieces, the connecting pieces have a particular shape in order to improve positive engagement. An axially inwardly open annular gap, which is filled by the elastic basic member material, is provided on the outer periphery.
German Patent Document No. 82 21 412 U1 describes a torsion shaft having a configuration of the generic type. Here the connecting pieces are joined by positive engagement to the basic member of the shaft. To enhance the joining strength, the connecting pieces can be adhesively bonded to the basic member.
An object of the present invention is to provide a shaft that is compact, functions reliably, and can be manufactured efficiently. xe2x80x9cFunctions reliablyxe2x80x9d means in particular that even if there is a radially small enclosure of the connector pieces in the elastic basic member material of the shaft, prevention of any rotation of the connector pieces within the shaft basic member is still guaranteed. Axial displaceability of the connector pieces within the shaft basic member material is also to be ruled out with assurance, with minimal material outlay for the basic member. Secure joining of the parts to be joined to one another is at least to require no additional manufacturing effort, but rather to reduce as much as possible that effort that had to be exerted in the case of the existing generic parts.
The present invention therefore provides a shaft, in particular a drive shaft, for transferring torques, having a basic member made of an elastic first plastic material, and connecting pieces, shaped at their ends into the basic member and prevented by positive engagement from rotating and displacing axially, made of a less-elastic or inelastic second plastic material, characterized in that both materials are crosslinked with one another at the interfaces of the parts (1, 2) constituted by them.
The present invention employs the concept of preventing the connector pieces from rotating and displacing within the basic member material of the shaft not only by positive engagement, but also by way of a chemical bond between the materials to be joined together. Plastics which allow chemical bonds of this kind during the production of assembled parts are known.
Thermoplastics, in particular, are suitable.